Indwelling needle devices are used widely for procedures such as infusion, blood transfusion, extracorporeal blood circulation and the like, and various configuration examples of the same are known. For example, a winged indwelling needle has a configuration where a needle is held at a front end of a hub that has wing parts, and an infusion tube is attached to a rear end of the hub. During infusion, the wing parts are fastened onto the patient's arm or the like by adhesion tapes or the like so as to maintain the insertion of the needle.
Meanwhile, contamination and infection due to accidental punctures of injection needles, insertion needles and the like have been a problem in medical centers. As a structure for preventing an accidental puncture, a structure has been known where a cylindrical shield having wing parts is provided slidably with respect to a hub having a needle. That is, by sliding the cylindrical shield, the needle either can be exposed or housed in the shield, and when the injection needle and the insertion needle are discarded after use, each of them can be slid into the shield so as to be housed therein.
Further, when a metal needle is indwelled in a blood vessel, the blood vessel is damaged in some cases. As a structure to cope with this, the following structure of an indwelling needle has been known; the structure includes a flexible outer needle and a rigid inner needle that are configured so that insertion is carried out with use of the inner needle projected out of the outer needle and thereafter the inner needle can be retracted through the outer needle. In this case also, to prevent an accidental puncture, the foregoing structure combined with a cylindrical shield as described above has been known also, which allows the inner needle to be housed in the cylindrical shield in a state where the outer needle is indwelled.
In the indwelling needle of the double-needle structure, which includes the above-described cylindrical shield for preventing an accidental puncture, an infusion tube is connected with a hub that holds the inner needle. In a state in which the inner needle is retracted into the cylindrical shield, a flow path from the infusion tube to a lumen of the outer needle passes a lumen of the inner needle. The lumen of the inner needle, however, has a small diameter, and this makes it difficult to provide a sufficient flow rate.
To provide a sufficient flow rate, it has been attempted to utilize a space formed between an outer peripheral surface of the hub that holds the inner needle and an inner peripheral surface of the cylindrical shield as a flow path to be added to the flow path formed by the lumen of the inner needle. In other words, it has been attempted to adopt a structure in which the space formed between the outer peripheral surface of the hub and the inner peripheral surface of the cylindrical shield communicates with the lumen of the outer needle via a gap between the outer needle and the inner needle, and an opening is formed in the hub so as to allow the foregoing space and the lumen of the hub to communicate with each other. Since it is possible to make the lumen of the hub broader than the lumen of the inner needle, an increased flow rate can be provided as a whole as compared with the flow rate in the case where only the lumen of the inner needle is available as a flow path (see, e.g., Patent Document 1).
Patent document 1: JP 2001-245980 A